U.S. patent application number 10/588600 was filed with the patent office on 2007-06-28 for gas turbine engine provided with a foreign matter removal passage.
This patent application is currently assigned to Honda Motor Co., Ltd.. Invention is credited to Masayuki Fukutani, Osamu Kawamoto, Hiroki Nagata, Mineyasu Oana.
Application Number | 20070144139 10/588600 |
Document ID | / |
Family ID | 36577759 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144139 |
Kind Code |
A1 |
Kawamoto; Osamu ; et
al. |
June 28, 2007 |
Gas turbine engine provided with a foreign matter removal
passage
Abstract
[Object] To provide a gas turbine engine which is simple in
structure but can effectively remove foreign matters from the
combustion air. [Means] The intake passage 21 includes an inlet
portion 29, a curved portion 30 and a reduced diameter portion 31.
The bypass duct 24 is curved away from the central axial line CL in
a region corresponding to the curved portion 30 and reduced
diameter portion 31 of the intake passage 29. Between the intake
passage 29 and bypass duct 24 is defined an annular space 32. In
the reduced diameter portion 31, the outer liner 20 is formed with
a large number of foreign matter introduction openings 33 in a
circumferential arrangement for communication between the intake
passage 21 and annular space 32. The inner casing 4 is formed with
a plurality of foreign matter ejection holes 34 in a
circumferential arrangement in a part thereof that curves outward
for communication between the annular space 32 and bypass duct
24.
Inventors: |
Kawamoto; Osamu; (Wako,
JP) ; Nagata; Hiroki; (Wako, JP) ; Fukutani;
Masayuki; (Wako, JP) ; Oana; Mineyasu; (Wako,
JP) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
14TH FLOOR
8000 TOWERS CRESCENT
TYSONS CORNER
VA
22182
US
|
Assignee: |
Honda Motor Co., Ltd.
|
Family ID: |
36577759 |
Appl. No.: |
10/588600 |
Filed: |
August 31, 2005 |
PCT Filed: |
August 31, 2005 |
PCT NO: |
PCT/JP05/15851 |
371 Date: |
August 7, 2006 |
Current U.S.
Class: |
60/39.092 |
Current CPC
Class: |
F05D 2260/607 20130101;
Y02T 50/60 20130101; F02K 3/06 20130101; F02C 7/052 20130101; F05D
2220/327 20130101; F05D 2220/326 20130101; F05D 2250/323 20130101;
F02C 7/05 20130101; F05D 2250/71 20130101 |
Class at
Publication: |
060/039.092 |
International
Class: |
F02C 7/052 20060101
F02C007/052 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2004 |
JP |
2004- 353187 |
Claims
1. A gas turbine engine provided with a foreign matter removal
passage, comprising: an outer casing; an inner casing received in
the outer casing so as to define a bypass duct having an annular
cross section in cooperation with the outer casing; an outer liner
received in the inner casing; an inner liner received in the outer
liner so as to define an intake passage in cooperation with the
outer liner; a first compressor provided in a downstream end of the
intake passage; a combustor connected to an outlet end of the first
compressor; a turbine provided adjacent to an outlet end of the
combustor; a rotary shaft rotatably received in the inner liner and
having a front fan attached to a front end thereof adjacent to both
an inlet end of the bypass duct and an inlet portion of the intake
passage, the rotary shaft further carrying a impeller wheel of the
first compressor and a turbine wheel of the turbine at appropriate
parts thereof; and a foreign matter removal passage communicating
with the intake passage via a plurality of foreign matter
introduction openings formed in the inner casing and with the
bypass duct via a plurality of foreign matter ejection openings
formed in the outer liner.
2. The gas turbine engine according to claim 1, wherein the intake
passage further comprises a curved portion connected to a
downstream end of the inlet portion and directed more toward an
axial line of the rotary shaft than the inlet portion and a reduced
diameter portion connected to a downstream end of the curved
portion and defining a part of the intake passage having a smallest
diameter with respect to the central axial line, and the foreign
matter introduction openings that communicate the intake passage
with the foreign matter removal passage are formed at least in a
part of the outer liner corresponding to the reduced diameter
portion.
3. The gas turbine engine according to claim 1, wherein the intake
passage further comprises a curved portion connected to a
downstream end of the inlet portion and directed more toward an
axial line of the rotary shaft than the inlet portion and a reduced
diameter portion connected to a downstream end of the curved
portion and defining a part of the intake passage having a smallest
diameter with respect to the central axial line, and the foreign
matter introduction openings that communicate the intake passage
with the foreign matter removal passage are formed at least in a
part of the outer liner corresponding to the curved portion.
4. The gas turbine engine according to claim 1, wherein the foreign
matter removal passage is defined between the inner casing and
outer liner at least in a region adjacent to the curved portion of
the intake passage.
5. The gas turbine engine according to claim 1, wherein the foreign
matter removal passage is defined between the inner casing and
outer liner at least in a region adjacent to the reduced diameter
portion of the intake passage.
6. The gas turbine engine according to claim 1, wherein the first
compressor comprises a centrifugal compressor.
7. The gas turbine engine according to claim 6, wherein an upstream
end of the intake passage is provided with a second compressor
comprising an axial flow compressor.
8. The gas turbine engine according to claim 1, wherein the foreign
matter introduction openings are formed in the outer liner in a
circumferential arrangement.
9. The gas turbine engine according to claim 1, wherein the foreign
matter introduction openings are each provided with an elongated
configuration selected from a group consisting of a slot, an
elliptic hole and a rectangular hole.
10. The gas turbine engine according to claim 9, wherein each
foreign matter introduction opening provided with an elongated
configuration has a lengthwise axis slanted with respect to the
central axial line.
11. The gas turbine engine according to claim 1, wherein the
foreign matter ejection holes are formed in the inner casing in a
circumferential arrangement.
12. The gas turbine engine according to claim 1, wherein the
foreign matter ejection holes are formed in a part of the inner
casing recessed from a general wall surface of the inner casing
facing the bypass duct.
13. The gas turbine engine according to claim 12, wherein the
recess part is covered by a lid plate which defines an opening in a
rear edge thereof
14. The gas turbine engine according to claim 1, wherein a part of
the bypass duct corresponding to the curved portion of the intake
passage curves radially outward.
Description
TECHNICAL FIELD
[0001] The present invention relates to a gas turbine engine
primarily for use in aircraft, and in particular to a technology
for preventing the intrusion of dust and water into the combustion
chamber.
BACKGROUND OF THE INVENTION
[0002] There are various types of gas turbine engine for use in
aircraft, but turbofan engines are by far most commonly used in
passenger planes and cargo planes. In a turbofan engine, the
combustion gas of the gas turbine is expelled rearward and a
propeller fan (front fan) provided immediately downstream of the
air inlet is driven by the drive shaft of the gas turbine engine.
In such a gas turbine engine, a large part of the air drawn into
the engine by the front fan is expelled from the rear end of the
engine as a propelling airflow while a remaining part of the air is
introduced into the combustion chamber of the gas turbine engine as
combustion air. In the turbofan engine, combustion gas of high
temperature and high pressure is produced by the compressor and the
combustion chamber provided in the front end of the engine, and is
forwarded to the turbine provided in the rear end of the engine to
drive the rotary shaft that integrally carries the impeller of the
compressor and front fan. The gas turbine is typically equipped
with a compressor of a centrifugal or axial flow type and an
annular combustion chamber having a large number of air inlet
holes.
[0003] In an aircraft gas turbine engine, because the air near the
ground is drawn into the air inlet as the aircraft takes off or
makes a landing, it is inevitable that the combustion air is mixed
with foreign matters. Such foreign matters included in the
combustion air may block the air inlet hole of the combustion
chamber and/or cause wear to the impeller of the turbine.
Therefore, it is desirable to install a countermeasure for removing
such foreign matters. A typical arrangement for removing foreign
matters in a gas turbine engine consists of a curved passage
provided immediately downstream of the diffuser of the centrifugal
compressor and a trap port provided in a radially outward part of
this passage for removing the foreign matters out of the passage as
disclosed in Japanese patent laid open publication No. 2002-242699
(Paragraphs 0017 and 0018, and FIG. 1). In this arrangement for
removing foreign matters, the foreign matters trapped by the trap
port are stored in a trap chamber, and the engine operator can
remove the foreign matters from the trap chamber by removing a plug
of the trap chamber when the engine is either not in operation or
in operation. It is also possible to provide a solenoid valve
instead of the plug to automatically remove the foreign matter
while the engine is in operation.
SUMMARY OF THE INVENTION
Tasks to be Achieved by the Invention
[0004] When the arrangement for removing foreign matters disclosed
in the mentioned Japanese patent laid open publication is applied
to an aircraft turbofan engine, the following problems associated
with the removal of foreign matters arise. Because a bypass passage
having an annular cross section for conducting an airflow for
propulsion is formed around the gas turbine, to gain access to the
plug of the trap chamber, it is necessary to dismantle the
surrounding casing. Therefore, large amounts of time and cost were
required when removing foreign matters. The use of a solenoid valve
that can automatically open and close eliminates the need to
dismantle the casing, but the necessary control system for
controlling the opening and closing of the solenoid valve adds to
the complexity of the system and the cost. Also, such a control
system could fail.
[0005] In view of such problems of the prior art, a primary object
of the present invention is to provide a gas turbine engine which
can effectively remove foreign matters from the combustion air
using a highly simple structure.
[0006] A second object of the present invention is to provide a gas
turbine engine which can remove foreign matters from combustion air
without substantially reducing the efficiency of the engine.
[0007] A third object of the present invention is to provide a gas
turbine engine which can remove foreign matters from combustion air
in a highly efficient manner.
Means to Achieve the Task
[0008] According to the present invention, at least some of these
objects can be accomplished by providing a gas turbine engine
provided with a foreign matter removal passage, comprising: an
outer casing; an inner casing received in the outer casing so as to
define a bypass duct having an annular cross section in cooperation
with the outer casing; an outer liner received in the inner casing;
an inner liner received in the outer liner so as to define an
intake passage in cooperation with the outer liner; a first
compressor provided in a downstream end of the intake passage; a
combustor connected to an outlet end of the first compressor; a
turbine provided adjacent to an outlet end of the combustor; a
rotary shaft rotatably received in the inner liner and having a
front fan attached to a front end thereof adjacent to both an inlet
end of the bypass duct and an inlet portion of the intake passage,
the rotary shaft further carrying a impeller wheel of the first
compressor and a turbine wheel of the turbine at appropriate parts
thereof; and a foreign matter removal passage communicating with
the intake passage via a plurality of foreign matter introduction
openings formed in the inner casing and with the bypass duct via a
plurality of foreign matter ejection openings formed in the outer
liner.
[0009] Thus, the foreign matters such as dust and water that may be
included in the combustion air flowing into the intake passage are
ejected to the bypass duct via the foreign matter removal passage,
and is expelled rearward out of the engine along with the
propulsion air. The combustion air is made free from foreign
matters and compressed so that the combustion efficiency can be
improved.
[0010] Preferably, the intake passage further comprises a curved
portion connected to a downstream end of the inlet portion and
directed more toward an axial line of the rotary shaft than the
inlet portion and a reduced diameter portion connected to a
downstream end of the curved portion and defining a part of the
intake passage having a smallest diameter with respect to the
central axial line, and the foreign matter introduction openings
that communicate the intake passage with the foreign matter removal
passage are formed at least in a part of the outer liner
corresponding to the reduced diameter portion or the curved
portion.
[0011] Thus, as the combustion air mixed with foreign matters flows
in the intake passage, owing to the inertia which is greater for
the foreign matters having a greater density than air, the foreign
matters tend to travel more straight than the air so that most of
the foreign matters that have been introduced into the intake
passage are selectively passed into the foreign matter removal
passage, and then to the bypass passage. Also, because the
configuration of the intake passage forces the combustion air
toward the rotary shaft, the combustion air can be efficiently
compressed and the combustion efficiency can be thereby
improved.
[0012] According to a preferred embodiment of the present
invention, the foreign matter removal passage is defined between
the inner casing and outer liner at least in a region adjacent to
the curved portion or reduced diameter portion of the intake
passage. Thereby, the passage arrangement for conducting the
foreign matters can be simplified, and the position and number of
the openings formed in the intake passage and bypass duct for
communication with the foreign matter removal passage can be
selected freely.
[0013] Typically, the first compressor comprises a centrifugal
compressor, and an upstream end of the intake passage is provided
with a second compressor comprising an axial flow compressor. If
the foreign matter introduction openings are formed in a part of
the outer liner corresponding to a part of the intake passage
extending into a front end of the first compressor, the pressure
produced by the first compressor helps the foreign matters to be
forced into the foreign matter removal passage. Also, if the first
compressor consists of a centrifugal compressor which has a front
end having a relatively small diameter and a rear end having a
relatively large diameter, by making a part of the bypass duct
corresponding to the curved portion of the intake passage curve
radially outward, a relatively large annular space can be defined
between the intake passage and bypass passage adjacent to the front
end of the first compressor, and it can be conveniently used as the
foreign matter removal passage.
[0014] If the foreign matter introduction openings are formed in
the outer liner in a circumferential arrangement, foreign matters
can be evenly removed from the combustion air. If the foreign
matter introduction openings are each provided with an elongated
configuration selected from a group consisting of a slot, an
elliptic hole and a rectangular hole, and each foreign matter
introduction opening provided with an elongated configuration has a
lengthwise axis slanted with respect to the central axial line,
relatively large foreign matters can be removed without unduly
reducing the rigidity of the outer liner.
[0015] If the foreign matter ejection holes are formed in the inner
casing in a circumferential arrangement, foreign matters can be
evenly removed from the combustion air that has flowed into the
foreign matter removal passage.
[0016] According to a preferred embodiment of the present
invention, the foreign matter ejection holes are formed in a part
of the inner casing recessed from a general wall surface of the
inner casing facing the bypass duct. Because the propulsion airflow
in the bypass duct produces a region of reduced pressure in such a
recessed part, the air mixed with foreign matter can be effectively
drawn from the foreign matter removal passage to the bypass duct.
This effect is particularly enhanced if the recess part is covered
by a lid plate which defines an opening in a rear edge thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Now the present invention is described in the following with
reference to the appended drawings, in which:
[0018] FIG. 1 is a simplified vertical sectional view of a jet
engine embodying the present invention;
[0019] FIG. 2 is an enlarged view of a part of FIG. 1 indicated by
II;
[0020] FIG. 3 is a developed view of an essential part of the outer
liner of the embodiment of the present invention;
[0021] FIG. 4 is a diagram showing a mode of operation of the
illustrated embodiment;
[0022] FIG. 5 is a vertical sectional view of a modified embodiment
of the present invention;
[0023] FIG. 6 is a developed view of an essential part of the outer
liner of another modified embodiment of the present invention;
and
[0024] FIG. 7 is a developed view of an essential part of the outer
liner of yet another modified embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Now the present invention is described in the following in
more detail in terms of a concrete embodiment with reference to the
appended drawings.
[0026] FIG. 1 is a simplified overall view of a turbofan engine
(which is referred to simply as "engine" hereinafter). This engine
1 comprises an outer casing 3 and an inner casing 4 which are both
cylindrical in shape and disposed in a mutually coaxial
relationship joined by straightening vanes 2. The engine 1 further
comprises a rotary shaft including an outer shaft 7 and an inner
shaft 8 which are centrally supported in the inner casing 4 by
mutually independent bearings 5f, 5r, 6f and 6r. "CL" in the
drawing denotes the central axial line (rotative axial line) of the
outer shaft 7 and inner shaft 8.
[0027] The outer shaft 7 is integrally provided with an impeller
wheel 9 for a high pressure centrifugal compressor (second
compressor means) HC at a front end thereof and a high pressure
turbine wheel 11 for a high pressure turbine HT, which is disposed
adjacent to the nozzle N of a combustor 10, at a rear end
thereof.
[0028] The inner shaft 8 is integrally provided with a front fan 12
at a front end thereof, a compressor wheel 13 incorporated with
rotor vanes of a low pressure axial flow compressor (first
compressor means) LC to the rear of the front fan 12 and a low
pressure turbine wheel 15, which is disposed in a jet duct 14 and
incorporated with rotor vanes for a low pressure turbine LT, at a
rear end thereof.
[0029] The front fan 12 is centrally provided with a nose cone 16.
To the rear of the front fan 12 are provided a plurality of stator
vanes 17 each having a radially outer end secured to an inner
circumferential surface of the outer casing 3.
[0030] Stator vanes 18 for the low pressure axial flow compressor
LC are attached to the inner casing 4 adjacent to a front end
thereof. To the rear of the low pressure axial flow compressor LC
is disposed an intake passage 21 defined by an inner liner 19 and
an outer liner 20 and having an annular cross section for
conducting the combustion air pre-compressed by the low pressure
axial flow compressor LC. The high pressure centrifugal compressor
HC is provided in a downstream end of the intake passage 21, and a
rear part of the outer liner 20 serves as the impeller casing for
the high pressure centrifugal compressor HC. To the inner periphery
of the intake passage 21 is attached a bearing box 23 that
accommodates the bearings 5f and 6f supporting the front ends of
the outer shaft 7 and inner shaft 8, respectively.
[0031] The air drawn by the front fan 12 is in part forwarded to
the low pressure axial flow compressor LC and then to the high
pressure centrifugal compressor HC. The remaining part of the drawn
air or a large part of the drawn air having a relatively low speed
is passed rearward through a bypass duct 24 defined between the
outer casing 3 and inner casing 4, and provides a primary thrust
force in a low speed range.
[0032] A diffuser 25 is attached to the outer periphery of the high
pressure centrifugal compressor HC to supply a high pressure air to
the combustor 10 disposed immediately downstream thereof.
[0033] The combustor 10 is of an annular type having a large number
of air inlet holes (not shown in the drawings). The fuel injected
from a fuel injection nozzle 26 provided in a rear end surface
thereof is mixed with the high pressure air forwarded from the
diffuser 25, and combusted in the combustor 10. A thrust is
produced by the combustion gas expelled, via the nozzle N that
faces rearward, from the jet duct 14 to the atmosphere. To the
inner periphery of the jet duct 14 is attached a bearing box 27
accommodating the bearings 5r and 6r supporting the rear ends of
the outer shaft 7 and inner shaft 8, respectively. To the outer
shaft 7 of the engine 7 is connected an output shaft of a starter
motor 28 via a gear box not shown in the drawings.
Foreign Matter Removal Passage
[0034] The foreign matter removal passage of the illustrated
embodiment is now described in the following primarily with
reference to FIG. 2 (an enlarged view of a part of FIG. 1 indicated
by II).
[0035] Referring to FIG. 2, the intake passage 21 includes an inlet
portion 29 provided with the stator vanes 18 of the low pressure
axial flow compressor LC, a curved portion 30 that curves inward
(or toward the central axial line CL) and a reduced diameter
portion 31 accommodating a front part of the impeller wheel 9 of
the high pressure centrifugal compressor HC. The inlet portion 29
has a larger diameter than the remaining part of the intake passage
21 and the reduced diameter portion 31 has a smaller diameter than
any other part of the intake passage. The curved portion 30 has a
diameter which progressively and smoothly decreases from the side
of the inlet portion 29 to the reduced diameter portion 31. The
reduced diameter portion extends substantially in parallel with the
central axial line, and connects to the inlet passage of the high
pressure centrifugal compressor HC. Meanwhile, the bypass duct 24
curves outward (or away from the central axial line CL) in a region
that corresponds to the curved portion 30 and reduced diameter
portion 31 of the intake passage 21. Between the intake passage 21
and bypass duct 24 in this region is defined an annular space 32
serving as the foreign matter removal passage. In the illustrated
embodiment, the inner diameter Do of the outer liner 20 in the
reduced diameter portion 31 is smaller than the outer diameter Di
of the inner liner 19 in the inlet portion 29.
[0036] The part of the outer liner 20 corresponding to the reduced
diameter portion 31 of the intake passage 21 is formed with a large
number (40, for instance) of foreign matter introduction holes 33
arranged in a circular pattern for communicating the intake passage
21 with the annular space 32. As shown in FIG. 3 (developed view of
an essential part of the outer liner 20), these foreign matter
introduction holes 33 are formed in the outer liner 20 as elongated
slots each having an lengthwise axis which is slanted by an angle
.theta. (50 to 60 degrees) with respect to the central axial line
CL. Also, because the airflow in the intake passage 21 has a
certain amount of circumferential component as indicated by arrows
A in FIG. 3, it is advantageous to slant the foreign matter
introduction holes 33 to extend substantially perpendicular to the
airflow.
[0037] The part of the inner casing 4 curving outward is likewise
provided with a number (6, for instance) of foreign matter ejection
holes 34 arranged in a circular pattern for communicating the
bypass duct 24 with the annular space 32. Each of the foreign
matter ejection holes 34 is formed in a part of the inner casing 4
facing the bypass duct 24 and formed with an individual recess 35,
and each recess 35 is provided with a cover plate 36 which
generally covers the recess 35 but defines an opening directed
downstream (rightward in FIG. 2) in the bypass duct 24. The
individual recesses 35 may be replaced by an annular recess common
to all of the foreign matter ejection holes 34.
Mode of Operation of the Embodiment
[0038] As the pilot activates the starter motor 28 in preparation
for a flight, the impeller wheel 9 of the high pressure centrifugal
compressor HC is actuated via the outer shaft 7, and high pressure
combustion air is forwarded to the combustor 10. The combustion air
is mixed with the fuel injected from the fuel injection nozzle 26,
and causes the combustion of the fuel, and the pressure of the
combustion gas drives the high pressure turbine wheel 11 of the
high pressure turbine HT and the low pressure turbine wheel 15 of
the low pressure turbine LT. The rotative power of the high
pressure turbine wheel 11 drives the impeller wheel 9 of the high
pressure centrifugal compressor HC while the rotative power of the
low pressure turbine wheel 15 drives the front fan 12 and the
compressor wheel 13 of the low pressure axial flow compressor LC.
The pressure of the combustion gas drives the high pressure turbine
wheel 11 and low pressure turbine wheel 15, and the engine 1
maintains a certain rotational speed which is determined by the
self-feedback balance between the supply of fuel and the volume of
intake air.
[0039] When the aircraft either takes off or makes a landing, air
containing foreign matters may be drawn from a region near the
ground into the engine 1. The air containing foreign matters 41 is
in part drawn into the intake passage 21 as combustion air as
indicated by the arrows in FIG. 4, and the remaining part of the
air is passed through the bypass duct 24 as propulsion air likewise
as indicated by the arrows. The combustion air that flows into the
inlet portion 29 of the intake passage 21 is pressurized by the low
pressure axial flow compressor LC, and flows toward the central
axial line along the cured portion 30 of the intake passage 21.
Because the foreign matters such as dust and water has a
substantially greater density than the combustion air, the foreign
matters tend to go straight into the inlet portion 29 of the intake
passage 21 until it hits the wall of the outer liner 20 and mostly
flows along the inner wall surface of the outer liner 20 as
indicated by the narrow arrows in FIG. 4.
[0040] The combustion air mostly flows from the intake passage 21
to the high pressure centrifugal compressor HC, but a small part of
the combustion air is diverted into the annular space 32 via the
foreign matter introduction holes 33 formed in the reduced diameter
portion 31. This owes to the fact that the inner pressure of the
annular space 32 is lower than that of the intake passage 21
because the annular space 32 communicates with the intake passage
21 at a relatively high pressure via the foreign matter
introduction holes 33 on the one hand and with the bypass duct 24
at a relatively low pressure via the foreign matter introduction
holes 34 on the other hand. As the combustion air is introduced
into the annular space 32 via the foreign matter introduction holes
33, foreign matters 41 that may have been carried by the combustion
air along the inner wall surface of the outer liner 20 is subjected
to a centrifugal force by the high pressure centrifugal compressor
HC, and are introduced into the annular space 32 via the foreign
matter introduction holes 33 along with a part of the combustion
air. Because each foreign matter introduction hole 33 consists of
an elongated slot, relatively large foreign matters can pass
through the foreign matter introduction holes 33 and introduced
into the annular space 32. Because the lengthwise axial line of
each foreign matter introduction hole 33 is slanted with respect to
the central axial line CL, almost all of the foreign matters 41
traveling along the inner wall surface of the outer liner 20 can be
trapped into the annular space 32.
[0041] Because the inner pressure of the annular space 32 is higher
than that of the bypass duct 24, the combustion air that has flowed
into the annular space 32 is expelled from the foreign matter
ejection holes 34 formed in the inner casing 4 along with the
foreign matters 41, and expelled rearward from the engine 1 as a
part of the propulsion air.
[0042] Owing to this arrangement described above, in the
illustrated embodiment, the combustion air which is to be
compressed in the high pressure centrifugal compressor HC is almost
totally free from foreign matters, and the problems of the prior
art such as the wear of the impeller wheel and blocking of the
combustor 10 can be avoided.
Modified Embodiments
[0043] Modified embodiments of the present invention are described
in the following.
[0044] FIG. 5 is a vertical sectional view of an essential part of
a modified embodiment, and FIGS. 6 and 7 are developed views of
essential parts of the outer liner 20 of other modified
embodiments. In the modified embodiment illustrated in FIG. 5, the
foreign matter introduction holes 33 are formed in the part of the
outer liner 20 corresponding to the curved portion 30 of the intake
passage 21. Each foreign matter introduction hole 33 is defined by
an edge of the outer liner 20 which is substantially in parallel
with the central axial line CL so that the airflow may flow into
the annular space 32 with a minimum resistance. The shape of each
hole is circular in the illustrated embodiment, but may also
consist of elongated holes such as those illustrated in FIGS. 2 and
3.
[0045] Also, as illustrated in FIG. 6, the foreign matter
introduction holes 33 may consist of elliptic holes each formed in
the outer liner 20 and having a lengthwise axial line which is
slanted by an angle .theta. (50 to 60 degrees) with respect to the
central axial line CL. The foreign matter introduction holes 33 may
also consist of rectangular holes as illustrated in FIG. 7. These
modified embodiments are application to those illustrated in FIGS.
2 and 5 in which the foreign matter introduction holes 33 are
formed in different parts of the intake passage 21.
[0046] The mode of operation of the modified embodiment illustrated
in FIG. 5 is not different from that of the preceding embodiment.
The foreign matters 41 that have traveled along the inner wall
surface of the outer liner 20 are introduced into the annular space
32 via the foreign matter introduction holes 33 along with the
combustion air. In this connection, it is preferable that the
foreign matter introduction holes 33 are formed in a region of the
outer liner 20 extending between the outer diameter line Di of the
inner liner in the inlet portion 29 and the reduced diameter
portion 31 as seen on a projection plane perpendicular to the
central axial line. For most of the foreign matters 41 that pass
through the inlet portion 29 to hit the outer liner 20 inside the
outer diameter line Di, it is advantageous to form the foreign
matter introduction holes 33 outward of the inner diameter line Do
and thereby increase the probability of the foreign matters 41 to
be introduced into the foreign matter introduction holes 33. Also,
if the foreign matter introduction holes 33 are formed more toward
the right than the reduced diameter portion 31 in FIG. 5, the
probability of the foreign matters 41 to flow into the high
pressure centrifugal compressor HC increases.
[0047] The present invention was described in terms of specific
embodiments, but the present invention is not limited by the
illustrated embodiments, and can be changed in various parts
thereof, such as the shapes and numbers of the foreign matter
introduction holes, foreign matter ejection holes and annular
space, can be changed without departing from the spirit of the
present invention. TABLE-US-00001 Glossary 1 engine 10 combustor 12
front fan 13 compressor wheel 19 inner liner 20 outer liner 21
intake passage 24 bypass duct 29 inlet portion 30 curved portion 31
reduced diameter portion 32 annular space (foreign matter removal
passage) 33 foreign matter introduction hole (foreign matter
removal passage) 34 foreign matter ejection hole (foreign matter
removal passage) 41 foreign matter CL central axial line
* * * * *